Generally, a computer system, for example a personal computer or high-end server, will install a cooling fan inside the system for heat dissipation. Particularly, for the existed central processing unit (CPU) or storage device, such as memory or hard disk, due to the increased processing speed and correspondingly the resulted high temperature, it is further required for employing a cooling fan to enhance the effect of heat dissipation to prevent the system damage due to being overheated.
Most of the prior arts employed the thermal diode, or DTS (Digital thermal Sensor), or PECI (Platform Environment Control Interface) provided by Intel Corp. to monitor the temperature of a device (such as CPU) and further control the cooling fan. When the temperature of the device is higher, it will control the fan to provide more airflow. For example, there are the Q-Fan Technology® provided by ASUSTeK Computer Inc., or Precision Cooling Technology®, and QST (Quiet System Technology®) provided by Intel Corp., in which PECI employs the on-die DTS to provide the digital information regarding to the temperature of a processor, and QST uses the PECI reading outputted by CPU as feedback to control the fan to make the temperature from a sensor approaching a Tcontrol value.
Also the U.S. Pat. No. 7,425,812 disclosed some known methods of fan control, particularly for the control of the time-variable rate of the rotation speed.